Reinforced Hollow Profiles

ABSTRACT

A hollow lineal profile formed from a continuous fiber reinforced ribbon (“CFRT”) that contains a plurality of continuous fibers embedded within a first thermoplastic polymer matrix. To enhance the tensile strength of the profile, the continuous fibers are aligned within the ribbon in a substantially longitudinal direction (e.g., the direction of pultrusion). In addition to continuous fibers, the hollow profile of the present invention also contains a plurality of long fibers that may be optionally embedded within a second thermoplastic matrix to form a long fiber reinforced thermoplastic (“LFRT”). The long fibers may be incorporated into the continuous fiber ribbon or formed as a separate layer of the profile. Regardless, at least at a portion of the long fibers are oriented at an angle (e.g., 90°) to the longitudinal direction to provide increased transverse strength to the profile.

RELATED APPLICATIONS

The present application claims priority as a divisional application ofU.S. patent application Ser. No. 13/698,375, filed on Feb. 12, 2013,which is a U.S. national stage filing of International PatentApplication No. PCT/US2011/041445, filed on Jun. 22, 2011, which claimspriority to Provisional Application Ser. No. 61/357,294, filed on Jun.22, 2010, all of which are incorporated by reference in their entiretiesherein.

BACKGROUND OF THE INVENTION

Hollow profiles have been formed by pulling (“pultruding”) continuousfibers through a resin and then shaping the fiber-reinforced resinwithin a pultrusion die. Because the profiles have continuous fibersoriented in the machine direction (longitudinal), they often exhibit ahigh tensile strength in the machine direction. The transverse strengthof such hollow profiles is, however, often poor, which can cause thematerial to split when a stress is applied in a cross-machine direction(transverse). In this regard, various attempts have been made tostrengthen hollow profiles in the transverse direction. For example,U.S. Pat. No. 7,514,135 to Davies, et al. describes a hollow part formedby providing a first layer of reinforcing rovings extending in alongitudinal pultrusion direction and forming a second layer on thefirst layer, the second layer containing at least some reinforcingfibers that extend in the transverse direction. One problem with thismethod, however, it is that it relies upon a thermoset resin to helpachieve the desired strength properties. Such resins are difficult touse during manufacturing and do not always possess good bondingcharacteristics for forming layers with other materials. Furthermore,the method described therein is also problematic in that it is difficultto apply the transverse fibers at selective locations (e.g., where theyare needed).

As such, a need currently exists for a hollow profile that exhibits goodtransverse strength and that can be made in a relatively efficient andsimple manner.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the present invention, a hollowlineal profile is disclosed. The profile comprises a consolidated ribbonthat contains a plurality of continuous fibers embedded within a firstthermoplastic matrix and substantially oriented in a longitudinaldirection. The profile also comprises a plurality of long fibers, atleast a portion of which are oriented at an angle relative to thelongitudinal direction. The ratio of the weight of the continuous fibersto the ratio of the weight of the long fibers is from about 0.2 to about10. Further, the ratio of flexural modulus to the maximum flexuralstrength of the profile is from about 50 to about 2200.

In accordance with another embodiment of the present invention, a methodfor forming a pultruded hollow profile is disclosed. The methodcomprises impregnating a plurality of continuous fibers with athermoplastic matrix within an extrusion device; consolidating theimpregnated fibers to form a first ribbon in which the continuous fibersare oriented in a longitudinal direction; pultruding the first ribbonand at least a second ribbon through a die to form the hollow profile,wherein the first ribbon, the second ribbon, or both contain longfibers.

Other features and aspects of the present invention are set forth ingreater detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof to one skilled in the art, is set forth moreparticularly in the remainder of the specification, including referenceto the accompanying figures, in which:

FIG. 1 is a schematic illustration of one embodiment of a pultrusionsystem that may be employed in the present invention;

FIG. 2 is a schematic illustration of one embodiment of an impregnationsystem for use in the present invention;

FIG. 3A is a cross-sectional view of the impregnation die shown in FIG.2;

FIG. 3B is an exploded view of one embodiment of a manifold assembly andgate passage for an impregnation die that may be employed in the presentinvention;

FIG. 3C is a perspective view of one embodiment of a plate at leastpartially defining an impregnation zone that may be employed in thepresent invention;

FIG. 4 is a side view of one embodiment of pre-shaping and pultrusiondies that may be employed in the present invention, wherein the flow ofthe continuous and long fiber materials are illustrated as they passthrough the dies;

FIG. 5 is a perspective view of the dies of FIG. 4;

FIG. 6 is a top view of one embodiment of a mandrel that may be employedin the present invention to shape the long fiber layer, wherein the flowof the long fiber material is also illustrated as it passes over themandrel;

FIG. 7 is a perspective view of the mandrel section of FIG. 6;

FIG. 8 is an exploded perspective view of one embodiment of a mandrelsection that may be employed in the present invention to shape thecontinuous fiber layer, wherein the flow of the continuous fibermaterial is also illustrated as it passes over the mandrel;

FIG. 9 is a perspective view of the mandrel section of FIG. 8;

FIGS. 10A and 10B are other perspective views of the mandrel section ofFIG. 8, in which FIG. 10A shows a right perspective view and FIG. 10Bshows a left perspective view of the mandrel section;

FIG. 11 is a cross-sectional view of one embodiment of a rectangular,hollow profile of the present invention;

FIG. 12 is a cross-sectional view of another embodiment of arectangular, hollow profile of the present invention;

FIG. 13 is side view of one embodiment of a pre-shaping and pultrusiondie system that may be employed to form the profile of FIG. 12;

FIG. 14 is perspective view of the pre-shaping and pultrusion die systemof FIG. 13;

FIG. 15 is a cross-sectional view of another embodiment of arectangular, hollow profile of the present invention;

FIG. 16 is a cross-sectional view of one embodiment of an L-shaped,hollow profile of the present invention; and

FIG. 17 is yet another embodiment of a rectangular, hollow profile ofthe present invention.

Repeat use of reference characters in the present specification anddrawings is intended to represent the same or analogous features orelements of the present invention.

DETAILED DESCRIPTION OF REPRESENTATIVE EMBODIMENTS Definitions

As used herein, the term “profile” generally refers to a pultruded part.The profile may possess a wide variety of cross-sectional shapes, suchas square, rectangular, circular, elliptical, triangular, I-shaped,C-shaped, U-shaped, J-shaped, L-shaped, slotted, etc. Such profiles maybe employed as a structural member for window lineals, decking planks,railings, balusters, roofing tiles, siding, trim boards, pipe, fencing,posts, light posts, highway signage, roadside marker posts, etc.

As used herein, the term “hollow” generally means that at least aportion of the interior of the profile is a voided space. The voidedspace may optionally extend the entire the length of the profile.

As used herein, the term “continuous fibers” generally refers to fibers,filaments, yarns, or rovings (e.g., bundles of fibers) having a lengththat is generally limited only by the length of the part. For example,such fibers may have a length greater than about 25 millimeters, in someembodiments about 50 millimeters or more, and in some embodiments, about100 millimeters or more.

As used herein, the term “long fibers” generally refers to fibers,filaments, yarns, or rovings that are not continuous and typically havea length of from about 0.5 to about 25 millimeters, in some embodiments,from about 0.8 to about 15 millimeters, and in some embodiments, fromabout 1 to about 12 millimeters.

DETAILED DESCRIPTION

It is to be understood by one of ordinary skill in the art that thepresent discussion is a description of exemplary embodiments only, andis not intended as limiting the broader aspects of the presentinvention.

Generally speaking, the present invention is directed to a hollow linealprofile formed from a continuous fiber reinforced ribbon (“CFRT”) thatcontains a plurality of continuous fibers embedded within a firstthermoplastic polymer matrix. To enhance the tensile strength andmodulus of the profile, the continuous fibers are aligned within theribbon in a substantially longitudinal direction (e.g., the direction ofpultrusion). In addition to continuous fibers, the hollow profile of thepresent invention also contains a plurality of long fibers that may beoptionally embedded within a second thermoplastic matrix to form a longfiber reinforced thermoplastic (“LFRT”). The long fibers may beincorporated into the continuous fiber ribbon or formed as a separatelayer of the profile. Regardless, at least a portion of the long fibersare oriented at an angle (e.g., 90°) relative to the longitudinaldirection to provide increased transverse strength to the profile.

To achieve a good balance between tensile strength and transversestrength, the present inventors have discovered that the relativeproportion of the continuous and long fibers may be selectivelycontrolled. Namely, the ratio of the weight of continuous fibers to theweight of long fibers is within the range of from about 0.2 to about 10,in some embodiments from about 0.4 to about 5, and in some embodiments,from about 0.5 to about 4. For instance, continuous fibers mayconstitute from about 10 wt. % to about 90 wt. %, in some embodimentsfrom about 20 wt. % to about 70 wt. %, and in some embodiments, fromabout 30 wt. % to about 60 wt. % of the profile. Likewise, long fibersmay constitute from about 0.5 wt. % to about 50 wt. %, in someembodiments from about 1 wt. % to about 40 wt. %, and in someembodiments, from about 2 wt. % to about 30 wt. % of the profile.

The resulting hollow profiles of the present invention may thereforeexhibit a relatively high maximum flexural strength (in the transversedirection) in comparison to profiles having the same shape and size, butlacking the long fiber reinforcement of the present invention. Forexample, the maximum flexural strength (also known as the modulus ofrupture or bend strength) may be about 12 Megapascals (“MPa”) or more,in some embodiments from about 15 to about 50 MPa, and in someembodiments, from about 20 to about 40 MPa. The term “maximum flexuralstrength” generally refers to the maximum stress reached on astress-strain curve produced by a “three point flexural” test (such asASTM D790-10, Procedure A or ISO 178) in the transverse direction atroom temperature. It represents the ability of the material to withstandan applied stress in the transverse direction to failure. Likewise, theprofile may also exhibit a high flexural modulus. The term “flexuralmodulus” generally refers to the ratio of stress to strain in flexuraldeformation (units of force per area), or the tendency for a material tobend. It is determined from the slope of a stress-strain curve producedby a “three point flexural” test (such as ASTM D790-10, Procedure A orISO 178). For example, the profile of the present invention may exhibita flexural modulus of about 2 Gigapascals (“GPa) or more, in someembodiments from about 2 to about 25 GPa, in some embodiments from about4 to about 20 GPa, and in some embodiments, from about 5 to about 15GPa.

The actual values for modulus and strength may of course vary dependingon the desired application. Nevertheless, the ratio of the flexuralmodulus to the maximum flexural strength typically falls within acertain range to achieve a part that exhibits a balance between tensilestrength and modulus properties, as well as transverse strength. Thisratio, for example, typically ranges from about 50 to about 2200, insome embodiments from about 100 to about 1000, in some embodiments fromabout 200 to about 800, and in some embodiments, from about 250 to about600.

The profile may also have a very low void fraction, such as about 3% orless, in some embodiments about 2% or less, and in some embodiments,about 1% or less. The void fraction may be determined in the mannerdescribed above, such as using a “resin burn off” test in accordancewith ASTM D 2584-08.

The continuous fibers employed in the hollow profile of the presentinvention may be formed from any conventional material known in the art,such as metal fibers; glass fibers (e.g., E-glass, A-glass, C-glass,D-glass, AR-glass, R-glass, S1-glass, S2-glass), carbon fibers (e.g.,graphite), boron fibers, ceramic fibers (e.g., alumina or silica),aramid fibers (e.g., Kevlar) marketed by E. I. duPont de Nemours,Wilmington, Del.), synthetic organic fibers (e.g., polyamide,polyethylene, paraphenylene, terephthalamide, polyethylene terephthalateand polyphenylene sulfide), and various other natural or syntheticinorganic or organic fibrous materials known for reinforcingthermoplastic compositions. Glass fibers and carbon fibers areparticularly desirable for use in the continuous fibers. Such fibersoften have a nominal diameter of about 4 to about 35 micrometers, and insome embodiments, from about 9 to about 35 micrometers. The fibers maybe twisted or straight. If desired, the fibers may be in the form ofrovings (e.g., bundle of fibers) that contain a single fiber type ordifferent types of fibers. Different fibers may be contained inindividual rovings or, alternatively, each roving may contain adifferent fiber type. For example, in one embodiment, certain rovingsmay contain continuous carbon fibers, while other rovings may containglass fibers. The number of fibers contained in each roving can beconstant or vary from roving to roving. Typically, a roving may containfrom about 1,000 fibers to about 50,000 individual fibers, and in someembodiments, from about 2,000 to about 40,000 fibers.

Any of a variety of thermoplastic polymers may also be employed to formthe first thermoplastic matrix in which the continuous fibers areembedded. Suitable thermoplastic polymers for use in the presentinvention may include, for instance, polyolefins (e.g., polypropylene,propylene-ethylene copolymers, etc.), polyesters (e.g., polybutyleneterephalate (“PBT”)), polycarbonates, polyamides (e.g., Nylon™),polyether ketones (e.g., polyetherether ketone (“PEEK”)),polyetherimides, polyarylene ketones (e.g., polyphenylene diketone(“PPDK”)), liquid crystal polymers, polyarylene sulfides (e.g.,polyphenylene sulfide (“PPS”)), fluoropolymers (e.g.,polytetrafluoroethylene-perfluoromethylvinylether polymer,perfluoro-alkoxyalkane polymer, petrafluoroethylene polymer,ethylene-tetrafluoroethylene polymer, etc.), polyacetals, polyurethanes,polycarbonates, styrenic polymers (e.g., acrylonitrile butadiene styrene(“ABS”)), and so forth. Polypropylene is a particularly suitablethermoplastic polymer.

The continuous fiber ribbon is generally formed in a manner to minimizeits void fraction and ensure good impregnation. In this regard, anextrusion device may be employed in the present invention to embed thecontinuous fibers into a thermoplastic matrix. Among other things, theextrusion device facilitates the ability of the thermoplastic polymer tobe applied to the entire surface of the fibers. For instance, the voidfraction may be about 3% or less, in some embodiments about 2% or less,and in some embodiments, about 1% or less. The void fraction may bemeasured using techniques well known to those skilled in the art. Forexample, the void fraction may be measured using a “resin burn off” testin which samples are placed in an oven (e.g., at 600° C. for 3 hours) toburn out the resin. The mass of the remaining fibers may then bemeasured to calculate the weight and volume fractions.

Such “burn off” testing may be performed in accordance with ASTM D2584-08 to determine the weights of the fibers and the thermoplasticmatrix, which may then be used to calculate the “void fraction” based onthe following equations:

V _(f)=100*(ρ_(t)−ρ_(c))/ρ_(t)

where,

V_(f) is the void fraction as a percentage;

ρ_(c) is the density of the composite as measured using knowntechniques, such as with a liquid or gas pycnometer (e.g., heliumpycnometer);

ρ_(t) is the theoretical density of the composite as is determined bythe following equation:

ρ_(t)=1/[W _(f)/ρ_(f) +W _(m)/ρ_(m)]

ρ_(m) is the density of the thermoplastic matrix (e.g., at theappropriate crystallinity);

ρ_(f) is the density of the fibers;

W_(f) is the weight fraction of the fibers; and

W_(m) is the weight fraction of the thermoplastic matrix.

Alternatively, the void fraction may be determined by chemicallydissolving the resin in accordance with ASTM D 3171-09. The “burn off”and “dissolution” methods are particularly suitable for glass fibers,which are generally resistant to melting and chemical dissolution. Inother cases, however, the void fraction may be indirectly calculatedbased on the densities of the thermoplastic polymer, fibers, and ribbonin accordance with ASTM D 2734-09 (Method A), where the densities may bedetermined ASTM D792-08 Method A. Of course, the void fraction can alsobe estimated using conventional microscopy equipment.

Referring to FIG. 2, one embodiment of an extrusion device is shown thatmay be employed for impregnating the fibers with a thermoplasticpolymer. More particularly, the apparatus includes an extruder 120containing a screw shaft 124 mounted inside a barrel 122. A heater 130(e.g., electrical resistance heater) is mounted outside the barrel 122.During use, a thermoplastic polymer feedstock 127 is supplied to theextruder 120 through a hopper 126. The thermoplastic feedstock 127 isconveyed inside the barrel 122 by the screw shaft 124 and heated byfrictional forces inside the barrel 122 and by the heater 130. Uponbeing heated, the feedstock 127 exits the barrel 122 through a barrelflange 128 and enters a die flange 132 of an impregnation die 150.

A continuous fiber roving 142 or a plurality of continuous fiber rovings142 are supplied from a reel or reels 144 to die 150. The rovings 142are generally kept apart a certain distance before impregnation, such asat least about 4 millimeters, and in some embodiments, at least about 5millimeters. The feedstock 127 may further be heated inside the die byheaters 133 mounted in or around the die 150. The die is generallyoperated at temperatures that are sufficient to cause melting andimpregnation of the thermoplastic polymer. Typically, the operationtemperatures of the die is higher than the melt temperature of thethermoplastic polymer, such as at temperatures from about 200° C. toabout 450° C. When processed in this manner, the continuous fiberrovings 142 become embedded in the polymer matrix, which may be a resin214 (FIG. 3A) processed from the feedstock 127. The mixture is thenextruded from the impregnation die 150 to create an extrudate 152.

A pressure sensor 137 (FIG. 3A) senses the pressure near theimpregnation die 150 to allow control to be exerted over the rate ofextrusion by controlling the rotational speed of the screw shaft 124, orthe federate of the feeder. That is, the pressure sensor 137 ispositioned near the impregnation die 150 so that the extruder 120 can beoperated to deliver a correct amount of resin 214 for interaction withthe fiber rovings 142. After leaving the impregnation die 150, theextrudate 152, or impregnated fiber rovings 142, may enter an optionalpre-shaping, or guiding section (not shown) before entering a nip formedbetween two adjacent rollers 190. Although optional, the rollers 190 canhelp to consolidate the extrudate 152 into the form of a ribbon (ortape), as well as enhance fiber impregnation and squeeze out any excessvoids. In addition to the rollers 190, other shaping devices may also beemployed, such as a die system. The resulting consolidated ribbon 156 ispulled by tracks 162 and 164 mounted on rollers. The tracks 162 and 164also pull the extrudate 152 from the impregnation die 150 and throughthe rollers 190. If desired, the consolidated ribbon 156 may be wound upat a section 171. Generally speaking, the ribbons are relatively thinand typically have a thickness of from about 0.05 to about 1 millimeter,in some embodiments from about 0.1 to about 0.8 millimeters, and in someembodiments, from about 0.2 to about 0.4 millimeters.

Within the impregnation die, it is generally desired that the rovings142 are traversed through an impregnation zone 250 to impregnate therovings with the polymer resin 214. In the impregnation zone 250, thepolymer resin may be forced generally transversely through the rovingsby shear and pressure created in the impregnation zone 250, whichsignificantly enhances the degree of impregnation. This is particularlyuseful when forming a composite from ribbons of a high fiber content,such as about 35% weight fraction (“Wf”) or more, and in someembodiments, from about 40% Wf or more. Typically, the die 150 willinclude a plurality of contact surfaces 252, such as for example atleast 2, at least 3, from 4 to 7, from 2 to 20, from 2 to 30, from 2 to40, from 2 to 50, or more contact surfaces 252, to create a sufficientdegree of penetration and pressure on the rovings 142. Although theirparticular form may vary, the contact surfaces 252 typically possess acurvilinear surface, such as a curved lobe, rod, etc. The contactsurfaces 252 are also typically made of a metal material.

FIG. 3A shows a cross-sectional view of an impregnation die 150. Asshown, the impregnation die 150 includes a manifold assembly 220, a gatepassage 270, and an impregnation zone 250. The manifold assembly 220 isprovided for flowing the polymer resin 214 therethrough. For example,the manifold assembly 220 may include a channel 222 or a plurality ofchannels 222. The resin 214 provided to the impregnation die 150 mayflow through the channels 222.

As shown in FIG. 3B, some portions of the channels 222 may becurvilinear, and in exemplary embodiments, the channels 222 have asymmetrical orientation along a central axis 224. Further, in someembodiments, the channels may be a plurality of branched runners 222,which may include first branched runner group 232, second group 234,third group 236, and, if desired, more branched runner groups. Eachgroup may include 2, 3, 4 or more runners 222 branching off from runners222 in the preceding group, or from an initial channel 222.

The branched runners 222 and the symmetrical orientation thereofgenerally evenly distribute the resin 214, such that the flow of resin214 exiting the manifold assembly 220 and coating the rovings 142 issubstantially uniformly distributed on the rovings 142. This desirablyallows for generally uniform impregnation of the rovings 142.

Further, the manifold assembly 220 may in some embodiments define anoutlet region 242, which generally encompasses at least a downstreamportion of the channels or runners 222 from which the resin 214 exits.In some embodiments, at least a portion of the channels or runners 222disposed in the outlet region 242 have an increasing area in a flowdirection 244 of the resin 214. The increasing area allows for diffusionand further distribution of the resin 214 as the resin 214 flows throughthe manifold assembly 220, which further allows for substantiallyuniform distribution of the resin 214 on the rovings 142.

As further illustrated in FIGS. 3A and 3B, after flowing through themanifold assembly 220, the resin 214 may flow through gate passage 270.Gate passage 270 is positioned between the manifold assembly 220 and theimpregnation zone 250, and is provided for flowing the resin 214 fromthe manifold assembly 220 such that the resin 214 coats the rovings 142.Thus, resin 214 exiting the manifold assembly 220, such as throughoutlet region 242, may enter gate passage 270 and flow therethrough, asshown.

Upon exiting the manifold assembly 220 and the gate passage 270 of thedie 150 as shown in FIG. 3A, the resin 214 contacts the rovings 142being traversed through the die 150. As discussed above, the resin 214may substantially uniformly coat the rovings 142, due to distribution ofthe resin 214 in the manifold assembly 220 and the gate passage 270.Further, in some embodiments, the resin 214 may impinge on an uppersurface of each of the rovings 142, or on a lower surface of each of therovings 142, or on both an upper and lower surface of each of therovings 142. Initial impingement on the rovings 142 provides for furtherimpregnation of the rovings 142 with the resin 214.

As shown in FIG. 3A, the coated rovings 142 are traversed in rundirection 282 through impregnation zone 250, which is configured toimpregnate the rovings 142 with the resin 214. For example, as shown inFIGS. 3A and 3C, the rovings 142 are traversed over contact surfaces 252in the impregnation zone.

Impingement of the rovings 142 on the contact surface 252 creates shearand pressure sufficient to impregnate the rovings 142 with the resin 214coating the rovings 142.

In some embodiments, as shown in FIG. 3A, the impregnation zone 250 isdefined between two spaced apart opposing plates 256 and 258. Firstplate 256 defines a first inner surface 257, while second plate 258defines a second inner surface 259. The contact surfaces 252 may bedefined on or extend from both the first and second inner surfaces 257and 259, or only one of the first and second inner surfaces 257 and 259.FIG. 3C illustrates the second plate 258 and the various contactsurfaces thereon that form at least a portion of the impregnation zone250 according to these embodiments. In exemplary embodiments, as shownin FIG. 3A, the contact surfaces 252 may be defined alternately on thefirst and second surfaces 257 and 259 such that the rovings alternatelyimpinge on contact surfaces 252 on the first and second surfaces 257 and259. Thus, the rovings 142 may pass contact surfaces 252 in a waveform,tortuous or sinusoidual-type pathway, which enhances shear.

The angle 254 at which the rovings 142 traverse the contact surfaces 252may be generally high enough to enhance shear, but not so high to causeexcessive forces that will break the fibers. Thus, for example, theangle 254 may be in the range between approximately 1° and approximately30°, and in some embodiments, between approximately 5° and approximately25°.

In alternative embodiments, the impregnation zone 250 may include aplurality of pins (not shown), each pin having a contact surface 252.The pins may be static, freely rotational, or rotationally driven. Infurther alternative embodiments, the contact surfaces 252 andimpregnation zone 250 may comprise any suitable shapes and/or structuresfor impregnating the rovings 142 with the resin 214 as desired orrequired.

To further facilitate impregnation of the rovings 142, they may also bekept under tension while present within the impregnation die. Thetension may, for example, range from about 5 to about 300 Newtons, insome embodiments from about 50 to about 250 Newtons, and in someembodiments, from about 100 to about 200 Newtons per roving 142 or towof fibers.

As shown in FIG. 3A, in some embodiments, a land zone 280 may bepositioned downstream of the impregnation zone 250 in run direction 282of the rovings 142. The rovings 142 may traverse through the land zone280 before exiting the die 150. As further shown in FIG. 3A, in someembodiments, a faceplate 290 may adjoin the impregnation zone 250.Faceplate 290 is generally configured to meter excess resin 214 from therovings 142. Thus, apertures in the faceplate 290, through which therovings 142 traverse, may be sized such that when the rovings 142 aretraversed therethrough, the size of the apertures causes excess resin214 to be removed from the rovings 142.

The impregnation die shown and described above is but one of variouspossible configurations that may be employed in the present invention.In alternative embodiments, for example, the fibers may be introducedinto a crosshead die that is positioned at an angle relative to thedirection of flow of the polymer melt. As the fibers move through thecrosshead die and reach the point where the polymer exits from anextruder barrel, the polymer is forced into contact with the fibers. Itshould also be understood that any other extruder design may also beemployed, such as a twin screw extruder. Still further, other componentsmay also be optionally employed to assist in the impregnation of thefibers. For example, a “gas jet” assembly may be employed in certainembodiments to help uniformly spread a bundle or tow of individualfibers, which may each contain up to as many as 24,000 fibers, acrossthe entire width of the merged tow. This helps achieve uniformdistribution of strength properties in the ribbon. Such an assembly mayinclude a supply of compressed air or another gas that impinges in agenerally perpendicular fashion on the moving fiber tows that passacross the exit ports. The spread fiber bundles may then be introducedinto a die for impregnation, such as described above.

Regardless of the technique employed, the continuous fibers are orientedin the longitudinal direction (the machine direction “A” of the systemof FIG. 1) to enhance tensile strength. Besides fiber orientation, otheraspects of the ribbon and pultrusion process are also controlled toachieve the desired strength. For example, a relatively high percentageof continuous fibers may be employed in the ribbon to provide enhancedstrength properties. For instance, continuous fibers typicallyconstitute from about 40 wt. % to about 90 wt. %, in some embodimentsfrom about 50 wt. % to about 85 wt. %, and in some embodiments, fromabout 55 wt. % to about 75 wt. % of the ribbon. Likewise, thermoplasticpolymer(s) typically constitute from about 10 wt. % to about 60 wt. %,in some embodiments from about 15 wt. % to about 50 wt. %, and in someembodiments, from about 25 wt. % to about 45 wt. % of the ribbon.

Furthermore, a combination of multiple continuous fibers ribbons may beemployed that are laminated together to form a strong, integratedstructure having the desired thickness. The number of ribbons employedmay vary based on the desired thickness and strength of the profile, aswell as the nature of the ribbons themselves. In most cases, however,the number of ribbons is from 2 to 40, in some embodiments from 3 to 30,and in some embodiments, from 4 to 25.

As stated above, the hollow profile also contains a plurality of longfibers optionally embedded within a second thermoplastic matrix. Thelong fibers may be formed from any of the material, shape, and/or sizeas described above with respect to the continuous fibers. Glass fibersand carbon fibers are particularly desirable for use as the long fibers.Furthermore, the second thermoplastic matrix in which the long fibersmay optionally be embedded may include a thermoplastic polymer, such asdescribed above. It should be understood that the first thermoplasticmatrix employed for the continuous fibers may be the same or differentthan the second thermoplastic matrix employed for the long fibers. Inone embodiment, for example, the long fibers are separately impregnatedwith a thermoplastic polymer, such as in a manner described below, andthereafter cooled and chopped into to pellets having a length of about25 millimeters or less. These pellets may be subsequently combined witha continuous fiber ribbon. Regardless, at least a portion of the longfibers in the hollow profile are oriented at an angle relative to thelongitudinal direction (i.e., pultrusion direction) to provide increasedtransverse strength. For example, about 10% or more, in some embodimentsabout 20% or more, and in some embodiments, about 30% or more of thefibers may be oriented at an angle relative to the longitudinaldirection. This angle may, for instance, be about 10° to about 120°, insome embodiments from about 20° to about 110° C., and in one embodiment,about 90°. This may be accomplished by intentionally orienting thefibers in the desired direction, or by random distribution.

The manner in which the long fibers and the continuous fiber ribbon arecombined together to form the hollow profile of the present inventionmay vary depending on the intended application and the locations of theprofile in which increased strength is required. In one embodiment, forexample, the long fiber material is formed as a separate layer from thecontinuous fiber ribbon. Among other things, this allows the long fibermaterial to be selectively added at only those locations where increasedtransverse strength is most needed.

Referring to FIG. 1, one particular embodiment of a system is shown inwhich one or more continuous fiber ribbons 12 are initially provided ina wound package on a creel 20. The creel 20 may be an unreeling creelthat includes a frame provided with horizontal rotating spindles 22,each supporting a package. A pay-out creel may also be employed,particularly if desired to induce a twist into the fibers. It shouldalso be understood that the ribbons may also be formed in-line with theformation of the profile. In one embodiment, for example, the extrudate152 exiting the impregnation die 150 from FIG. 2 may be directlysupplied to the system used to form a profile. A tension-regulatingdevice 40 may also be employed to help control the degree of tension inthe ribbons 12. The device 40 may include inlet plate 30 that lies in avertical plane parallel to the rotating spindles 22 of the creel 20. Thetension-regulating device 40 may contain cylindrical bars 41 arranged ina staggered configuration so that the ribbons 12 passes over and underthese bars to define a wave pattern. The height of the bars can beadjusted to modify the amplitude of the wave pattern and controltension.

If desired, the ribbons 12 may be heated in an oven 45 having any of avariety of known configuration, such as an infrared oven, convectionoven, etc. During heating, the fibers are unidirectionally oriented tooptimize the exposure to the heat and maintain even heat across theentire profile. The temperature to which the ribbons 12 are heated isgenerally high enough to soften the thermoplastic polymer to an extentthat the ribbons can bond together. However, the temperature is not sohigh as to destroy the integrity of the material. The temperature may,for example, range from about 100° C. to about 300° C., in someembodiments from about 110° C. to about 275° C., and in someembodiments, from about 120° C. to about 250° C. In one particularembodiment, for example, acrylonitrile-butadiene-styrene (ABS) is usedas the polymer, and the ribbons are heated to or above the melting pointof ABS, which is about 105° C. In another embodiment, polybutyleneterephalate (PBT) is used as the polymer, and the ribbons are heated toor above the melting point of PBT, which is about 224° C.

Upon being heated, the continuous fiber ribbons 12 may be provided to aconsolidation die to help bond together different ribbon layers, as wellas for alignment and formation of the initial shape of the profile.Referring to FIGS. 1, 4, and 5, for example, one embodiment of aconsolidation die 50 for use in forming a “hollow” profile is shown inmore detail. Although referred to herein as a single die, it should beunderstood that the consolidation die 50 may in fact be formed frommultiple individual dies (e.g., face plate dies). In this particularembodiment, the consolidation die 50 receives a first layer (orlaminate) 12 a of continuous fiber ribbons and a second layer (orlaminate) 12 b of continuous fiber ribbons at an inlet end 56. Theribbons within each layer are bonded together and guided throughchannels (not shown) of the die 50 in a direction “A”. The channels maybe provided in any of a variety of orientations and arrangements toresult in the desired reinforcement scheme. In the illustratedembodiment, for example, the layers 12 a and 12 b are initially spacedapart from each other in the vertical direction. As they pass throughthe channels of the die 50, the widths of the layers 12 a and/or 12 bare optionally ribbonred to help prevent pressure wedges, and to keepthe continuous fibers aligned and twist-free. Within the die 50, theribbons are generally maintained at a temperature at or above themelting point of the thermoplastic matrix used in the ribbon to ensureadequate consolidation.

Although not specifically shown in FIGS. 1, 4, and 5, a mandrel may alsobe provided in the interior of the consolidation die 50 to help guidethe laminates 12 a and 12 b into contact with each other on at least oneside of the profile. In the illustrated embodiment, for example, a sideportion 57 of the first layer 12 a and a side portion 53 of the secondlayer 12 b are angled so that they contact each other and form a side ofthe hollow profile. The other side of the profile is, however, typicallyleft open within the consolidation die 50 so that the discontinuousfiber material can be subsequently applied to the interior of theprofile in the pultrusion die. Of course, for those embodiments in whichthe discontinuous fiber material is not applied to the interior of thehollow profile, the consolidation die 50 may not be employed at all asthe entire profile can be optionally shaped within the pultrusion die.

When in the desired position, the layers 12 a and 12 b of continuousfiber material are pulled into a pultrusion die 60. It is generallydesired that the layers are allowed to cool briefly after exiting theconsolidation die 50 and before entering the pultrusion die 60. Thisallows the consolidated laminate to retain its initial shape beforeprogressing further through the system. Such cooling may be accomplishedby simply exposing the layers to the ambient atmosphere (e.g., roomtemperature) or through the use of active cooling techniques (e.g.,water bath or air cooling) as is known in the art. In one embodiment,for example, air is blown onto the layers (e.g., with an air ring). Thecooling between these stages, however, generally occurs over a smallperiod of time to ensure that the layers are still soft enough to befurther shaped. For example, after exiting the consolidation die 50, thelayers may be exposed to the ambient environment for only from about 1to about 20 seconds, and in some embodiments, from about 2 to about 10seconds, before entering the second die 60.

The configuration of the pultrusion die 60 depends in part on thedesired shape and properties for the resulting profile. For hollowprofiles, for example, the pultrusion die often contains a mandrelwithin its interior so that the fiber material flows between theinterior surface of the die and the external surface of the mandrel toform the desired shape. Solid profiles, however, are typically formedwithout a mandrel. Further, although referred to herein as a single die,it should be understood that the pultrusion die 60 may be formed frommultiple individual dies. In fact, the pultrusion die may preferablyemploy a first die section in which the discontinuous material issupplied and shaped a second die section in which the continuous fibermaterial is shaped. In FIGS. 4-5, for example, a first die section 62 isemployed that supplies and shapes discontinuous fiber material 61 and asecond die section 64 is employed that shapes the continuous fiberlayers 12 a and 12 b.

The particular manner in which the long fiber material 61 is supplied tothe first die section 62 is shown in more detail in FIGS. 6-8. As shown,a long fiber material 61 enters the first die section 62 and is curvedinto its interior cavity. Although not required, such a curved inletallows the long fiber material 61 to gradually flow into in thedirection “A” and toward a die outlet 67. In such embodiments, the angleβ at which the long fiber material is provided relative to the flowdirection “A” of the continuous fiber layers 12 a and 12 b may generallyvary, but is typically about 45° or more, in some embodiments about 60°or more, and in some embodiments, from about 75° to about 90°. Incertain cases, a non-perpendicular flow angle may be advantageousbecause it minimizes or overcomes backpressure in the die that may becaused by the high pressure flow of the long fiber material, which cansometimes lead to an undesirable backflow. The angled input orientationof the long fiber material, in combination with its curvedconfiguration, may also reduce the likelihood that static spots (deadspots) may form inside the die, which may cause resin degradation, fiberhang-up, or breakage.

Upon entering the first die section 62, the discontinuous material 61also flows over a mandrel 68. The mandrel 68 may be supported in acantilever manner so that it resists the forward force of the continuousmaterial being pulled around and over the mandrel. Further, although theentire mandrel is not shown herein, it should be understood that it maynevertheless extend into the aforementioned consolidation die 50 to help“pre-shape” the continuous fiber material in the manner described above.Regardless, the mandrel 68 shown in FIGS. 6-8 possesses multiplesections for accomplishing the desired shaping of the profile. Moreparticularly, the mandrel 68 contains a first mandrel section 69 that issolid and generally rectangular in cross-section. Thus, thediscontinuous material 61 passes over and around the mandrel section 69from its proximal end 71 to its distal end 73. In doing so, the material61 assumes the shape defined between the interior surface of the firstdie section 62 and an external surface 75 of the mandrel section 69,which in this embodiment, is a hollow rectangular shape.

The final shape of the continuous fiber layer is formed in the seconddie section 64 of the pultrusion die 60, over and around a secondsection 79 of the mandrel 68 as shown in FIGS. 9-10. The second mandrelsection 79 contains a U-shaped recess 103 that engages a protrusion 77of the first mandrel section 69 for connecting thereto. In thisembodiment, the second mandrel section 79 also contains an upper wall 83and lower wall 85 that are generally perpendicular to the direction “A”of material flow. An upwardly facing surface 91 intersects a curved edge93 of the upper wall 83 and slopes axially in the direction “A”.Similarly, a downwardly facing surface 95 intersects a curved edge ofthe lower wall 85 and slopes axially in the direction “A”. The surfaces91 and 95 both converge at an edge 97. During formation of the profile,the first layer 12 a of continuous fiber material is pulled over thesurface 91 and assumes the shape defined between an interior surface ofthe pultrusion die 60 and the upper wall 83. The second layer 12 b ofcontinuous fiber material is pulled over the surface 95 and likewiseassumes the shape defined between an interior surface of the pultrusiondie 60 and the lower wall 85. The layer 12 a and 12 b are also graduallypulled into contact with each other at the edge 97 to form one side ofthe resulting profile. If necessary, the materials may be subjected to asubsequent compression step, such as in a land die section (not shown),to further increase the degree of adhesion between the layers at theiredges.

Within the die 60, the ribbons are generally maintained at a temperaturewell above the melting point of the thermoplastic matrix used in theribbon to facilitate the ability to shape the part and intermix togetherthe discontinuous fiber material. However, the temperature is not sohigh as to destroy the integrity of the material. The temperature may,for example, range from about 100° C. to about 350° C., in someembodiments from about 120° C. to about 320° C., and in someembodiments, from about 150° C. to about 300° C.

If desired, the resulting profile may also be applied with a cappinglayer to enhance the aesthetic appeal of the profile and/or protect itfrom environmental conditions. Referring to FIG. 1, for example, such acapping layer may be applied via an extruder oriented at any desiredangle to introduce a thermoplastic resin into a capping die 72. Theresin may contain any suitable thermoplastic polymer known in the artthat is generally compatible with the thermoplastic polymer used to formthe profile. Suitable capping polymers may include, for instance,acrylic polymers, polyvinyl chloride (PVC), polybutylene terephthalate(PBT), ABS, polyolefins, polyesters, polyacetals, polyamids,polyurethanes, etc. Although the capping resin is generally free offibers, it may nevertheless contain other additives for improving thefinal properties of the profile. Additive materials employed at thisstage may include those that are not suitable for incorporating into thecontinuous fiber or long fiber layers. For instance, it may be desirableto add pigments to the composite structure to reduce finishing labor ofshaped articles, or it may be desirable to add flame retardant agents tothe composite structure to enhance the flame retarding features of theshaped article. Because many additive materials are heat sensitive, anexcessive amount of heat may cause them to decompose and producevolatile gases. Therefore, if a heat sensitive additive material isextruded with an impregnation resin under high heating conditions, theresult may be a complete degradation of the additive material. Additivematerials may include, for instance, mineral reinforcing agents,lubricants, flame retardants, blowing agents, foaming agents,ultraviolet light resistant agents, thermal stabilizers, pigments, andcombinations thereof. Suitable mineral reinforcing agents may include,for instance, calcium carbonate, silica, mica, clays, talc, calciumsilicate, graphite, calcium silicate, alumina trihydrate, bariumferrite, and combinations thereof.

While not shown in detail herein, the capping die 72 may include variousfeatures known in the art to help achieve the desired application of thecapping layer. For instance, the capping die 72 may include an entranceguide that aligns the incoming profile. The capping die may also includea heating mechanism (e.g., heated plate) that pre-heats the profilebefore application of the capping layer to help ensure adequate bonding.

Following optional capping, the shaped part 15 is then finally cooledusing a cooling system 80 as is known in the art. The cooling system 80may, for instance, be a vacuum sizer that includes one or more blocks(e.g., aluminum blocks) that completely encapsulate the profile while avacuum pulls the hot shape out against its walls as it cools. A coolingmedium may be supplied to the sizer, such as air or water, to solidifythe profile in the correct shape.

Vacuum sizers are typically employed when forming the profile. Even if avacuum sizer is not employed, however, it is generally desired to coolthe profile after it exits the capping die (or the consolidation orcalibration die if capping is not applied). Cooling may occur using anytechnique known in the art, such a vacuum water tank, cool air stream orair jet, cooling jacket, an internal cooling channel, cooling fluidcirculation channels, etc. Regardless, the temperature at which thematerial is cooled is usually controlled to achieve optimal mechanicalproperties, part dimensional tolerances, good processing, and anaesthetically pleasing composite. For instance, if the temperature ofthe cooling station is too high, the material might swell in the tooland interrupt the process. For semi-crystalline materials, too low of atemperature can likewise cause the material to cool down too rapidly andnot allow complete crystallization, thereby jeopardizing the mechanicaland chemical resistance properties of the composite. Multiple coolingdie sections with independent temperature control can be utilized toimpart the optimal balance of processing and performance attributes. Inone particular embodiment, for example, a vacuum water tank is employedthat is kept at a temperature of from about 10° C. to about 50° C., andin some embodiments, from about 15° C. to about 35° C.

As will be appreciated, the temperature of the profile as it advancesthrough any section of the system of the present invention may becontrolled to yield optimal manufacturing and desired final compositeproperties. Any or all of the assembly sections may be temperaturecontrolled utilizing electrical cartridge heaters, circulated fluidcooling, etc., or any other temperature controlling device known tothose skilled in the art.

Referring again to FIG. 1, a pulling device 82 is positioned downstreamfrom the cooling system 80 that pulls the finished profile 16 throughthe system for final sizing of the composite. The pulling device 82 maybe any device capable of pulling the profile through the process systemat a desired rate. Typical pulling devices include, for example,caterpillar pullers and reciprocating pullers. If desired, one or morecalibration dies (not shown) may also be employed. Such dies containopenings that are cut to the exact profile shape, graduated fromoversized at first to the final profile shape. As the profile passestherethrough, any tendency for it to move or sag is counteracted, and itis pushed back (repeatedly) to its correct shape. Once sized, theprofile may be cut to the desired length at a cutting station (notshown), such as with a cut-off saw capable of performing cross-sectionalcuts.

One embodiment of the hollow profile formed from the method describedabove is shown in more detail in FIG. 11 as element 16. As illustrated,the hollow profile 16 has a generally rectangular shape. An inner layer4 is formed by the LFRT material that extends around the entire profileand defines an interior surface 5. An outer layer 6 is likewise formedby the CFRT material that extends around the perimeter of the innerlayer 4 and positioned adjacent thereto. The thickness of these layersand the relative proportion of the LFRT and CFRT materials may bestrategically selected to help achieve a particular tensile strength andtransverse strength (e.g., flexural modulus) for the profile. Forexample, higher percentages of LFRT material (and/or thickness)generally result in higher transverse strength, while higher percentagesof CFRT material (and/or thickness) generally result in higher tensilestrength. To optimize these properties, the ratio of the weight of theCFRT layer to the weight of the LFRT layer is typically from about 0.2to about 10, in some embodiments from about 0.4 to about 5, and in someembodiments, from about 0.5 to about 4. In this regard, the thickness ofthe inner layer 4 may be from about 0.1 to about 2.0 millimeters, insome embodiments from about 0.5 to about 1.5 millimeters, and in someembodiments, from about 0.6 to about 1.2 millimeters, and the thicknessof the outer layer 6 may be from about 0.2 to about 4.0 millimeters, insome embodiments from about 0.5 to about 3.0 millimeters, and in someembodiments, from about 1.0 to about 2.0 millimeters. The totalthickness of the layers 4 and 6 may likewise be from about 1.0 to about4.0 millimeters, and in some embodiments, from about 2.0 to about 3.0millimeters.

The profile 16 of FIG. 11 also includes a capping layer 7 that extendsaround the perimeter of the outer layer 6 and defines an externalsurface 8 of the profile 16. The thickness of the capping layer 7depends on the intended function of the part, but is typically fromabout 0.1 to about 5 millimeters, and in some embodiments, from about0.2 to about 3 millimeters.

In the embodiments described and shown above, the LFRT material ispositioned around substantially the entire interior perimeter of theprofile. However, it should be understood that this is not required, andthat it may be desired in certain applications to apply the materialonly to specific locations that are advantageous according to aparticular design. One example of such a profile is shown in more detailin FIG. 12. As illustrated, the profile 216 generally has a hollow,rectangular shape. In this embodiment, an inner layer 206 is formed bythe CFRT material that extends around the entire profile and defines aninterior surface 205. The thickness of the layer 206 may be similar tothe CFRT layer described above with reference to FIG. 11. Contrary tothe embodiment of FIG. 11, however, the profile 216 does not contain acontinuous LFRT layer. Instead, LFRT material is located at discretelayers 204 at upper and lower surfaces 208 and 209 of the profile 216.Such discrete placement of the LFRT material may provide enhancedtransverse strength at only those locations where it is needed for aparticular application. A capping layer 207 may cover the periphery ofthe profile 216.

FIGS. 13-14 illustrate one embodiment of the consolidation die 250 andpultrusion die 260 that may be employed to form the profile 216. Similarto the embodiments described above, the consolidation die 250 in thisembodiment receives a first layer 212 a and second layer 212 b ofcontinuous fiber material at an inlet end 256. The layers 212 a and 212b are guided through channels (not shown) of the die 250 in a direction“A”. As they pass through the channels, the widths of the layers 212 aand/or 212 b are optionally ribbonred and connected at one side asdescribed above. When in the desired position, the layers 212 a and 212b are pulled into the pultrusion die 260, which employs a first diesection 262, a second die section 264, and a mandrel 268 that extendstherethrough. Together, each of these components helps shape thecontinuous fiber material. More particularly, as the continuous fiberlayers pass over and around the mandrel 268 from its proximal to distalend, they assume the shape defined between the interior surface of thedie 260 and an external surface of the mandrel, which in thisembodiment, is a hollow rectangular shape. The long fiber material 281is then introduced into a third die section 280 via an inlet portion,which is typically in the form of a cross-head die that extrudes thematerial at an input angle as mentioned above. In this particularembodiment, however, the long fiber material 281 is split into an upperstream 240 and a lower stream 242 within the third die section 280. Asthe streams 240 and 242 converge in the direction “A” of the materialflow and are pulled through the die system, they form the upper andlower discrete layers 204, respectively, of the profile 216. A cappinglayer 207 may then be applied using a capping die 272 as shown.

Of course, other hollow profiles may be formed in the present invention.Referring to FIG. 15, for example, another embodiment of a generallyrectangular, hollow profile 316 is shown in more detail. In thisparticular embodiment, an inner layer 304 is formed by the LFRT materialthat extends around the entire profile and defines an interior surface305. The thickness of the layer 304 may be similar to the long fiberlayer described above with reference to FIG. 11. Contrary to theembodiment of FIG. 11, however, the profile 316 does not contain a CFRTlayer around the entire periphery of the profile. Instead, the CFRTmaterial is provided as a discrete vertical layer 306 a and horizontallayer 306 b within the interior of the profile 316. A capping layer 307is likewise provided that extends around the periphery of the innerlayer 304 and defines an external surface 308 of the profile 316.

Still another embodiment of a hollow profile is shown in FIG. 16. Inthis embodiment, the profile 416 has a generally L-shaped cross-section.An inner layer 406 of the L-shaped profile 416 may include the CFRTmaterial and an outer layer 404 may include the LFRT material. Discretelayers 409 of CFRT material may also be employed. Further, a cappinglayer 407 may extend around the entire periphery of the profile 416 anddefine an external surface 408 thereof.

The embodiments described above contain the LFRT and CFRT materials inseparate layers so that selective reinforcement may be provided to theprofile. However, this is by no means required. In fact, in certainembodiments of the present invention, the long fiber material isintegrated into the continuous fiber ribbon so that the materials arenot provided as separate layers. This may be accomplished, for instance,by incorporating the long fiber material into the continuous ribbonduring impregnation.

Referring again to FIGS. 2-3, for example, long fiber pellets (notshown) containing a plurality of long fibers randomly distributed withina second thermoplastic matrix may be supplied to the hopper 126 andcombined with the first thermoplastic matrix 127. In this manner, thelong fiber pellets are melt-blended with the first thermoplastic matrixused to impregnate the continuous fiber strands and create an extrudate152 that contains continuous fibers, long fibers, and two differentthermoplastic matrices, which may include the same or differentpolymers. In the alternative, the long fibers may be added directly tothe hopper 126 without being pre-embedded with a thermoplastic matrix.In such embodiments, the first thermoplastic matrix will encapsulateboth the continuous and long fibers. Regardless of the techniqueemployed, however, the long fiber material may be distributed in asubstantially homogeneous manner throughout the profile. One example ofsuch a profile is shown in FIG. 17 as element 516. In this embodiment,the profile 516 is generally rectangular in shape and contains acontinuous fiber ribbon 514 within which is distributed a plurality oflong fibers 518. A capping layer 519 also extends around the perimeterof the ribbon 514 and defines an external surface of the profile 516. Itshould also be understood that such “hybrid” ribbons, which contain bothcontinuous and long fibers, may also be combined with one or moreadditional ribbons as described above. These additional ribbons maycontain continuous fibers, long fibers, or combinations thereof, and maybe pre-manufactured or made in line.

As will be appreciated, the particular profile embodiments describedabove are merely exemplary of the numerous designs that are madepossible by the present invention. Among the various possible profiledesigns, it should be understood that additional layers of continuousand/or long fiber material may be employed in addition to thosedescribed above. Further, the embodiments described above are generallyconsidered “lineal” profiles to the extent that they possess across-sectional shape that is substantially the same along the entirelength of the profile. It should be understood, however, that profilesmay also be formed in the present invention that have a varyingcross-sectional shape, such as curved, twisted, etc.

The present disclosure may be better understood with reference to thefollowing example.

Example

Continuous fiber ribbons were initially formed using an extrusion systemas substantially described above and shown in FIGS. 2-3. Glass fiberrovings (E-glass, 2200 tex) were employed for the continuous fibers witheach individual ribbon containing three (3) fiber rovings. Thethermoplastic polymer used to impregnate the fibers was acrylonitrilebutadiene styrene (ABS), which has a melting point of about 105° C. Eachribbon contained 60 wt. % glass fibers and 40 wt. % ABS. The resultingribbons had a thickness of between 0.2 to 0.4 millimeters and a voidfraction of less than 1%. Once formed, the ribbons were then fed to anextrusion/pultrusion line operating at a speed of 5 feet per minute.Prior to consolidation, the ribbons were heated within an infrared oven(power setting of 160). The heated ribbons were then supplied to aconsolidation die having a U-shaped channel that received the ribbonsand consolidated them together while forming the initial shape of theprofile. Within the die, the ribbons remained at a temperature of about121° C., just above the melting point of the ABS matrix. Uponconsolidation, the resulting laminate was then briefly cooled withambient air. The laminate was then passed through the pultrusion die asshown in FIG. 1. Long fiber pellets were applied to the interior sectionof the U-shaped profile at 246° C.

The resulting part was then supplied to a 1-inch land section to impartthe final “U shape” and cooled using an oil cooled sizing unit set at atemperature of about 26° C. Air cooling was then employed to completethe cooling process. The profile had a thickness of approximately 3.2millimeters and a width of approximately 40 millimeters. While thisparticular part formed had a U-shape, it should be understood that asubstantially rectangular hollow profile may simply be formed from twodifferent U-shaped laminates in the manner described above and shownherein.

Ten (10) different U-shaped profile samples were formed as describedabove with different amounts of continuous fibers and long fibers. Theamount of long fibers was varied by using different percentages of longfibers in the pellets, ranging from 0 wt. % to 40.%, and the amount ofcontinuous fibers was varied by using different numbers of ribbons,ranging from 2 to 7. The manner in which each of the samples was formedis reflected below in Table 1.

TABLE 1 Wt Ratio of Long Fibers Number of Continuous Fiber in PelletsContinuous Material to Long Sample (wt. %) Fiber Ribbons Fiber Material1 0 7 — 2 20 2 1.21 3 20 3 1.99 4 20 4 3.20 5 30 2 0.72 6 30 3 1.54 7 304 2.34 8 40 2 0.57 9 40 3 0.95 10 40 4 1.52

To determine the strength properties of the U-shaped profile,three-point flexural testing was performed in accordance with ASTMD790-10, Procedure A. One transverse edge of the profile was supportedwith a fixture, and the load from the Instron meter was applied to thefree edge of the U profile. The following equation was used to calculatethe maximum stress load on the part: Maximum stressload=(6*P_(max)*L)/w*t² where P_(max)=maximum load, L=length of leverarm, w=sample width, t=sample thickness. The strength properties of thesamples are set forth below in Table 2.

TABLE 2 Ratio of Maximum Flexural Flexural Flexural Modulus StrengthModulus to Flexural Sample (MPa) (GPa) Strength 1 11.73 26.6 2268 235.39 6.2 175 3 32.36 8.7 269 4 32.76 13.7 418 5 30.94 7.87 254 6 27.1713.55 499 7 26.57 14.87 560 8 27.93 11.82 423 9 26.57 13.75 518 10 29.6614.75 497

It should be understood that the strength properties of the U-shapedparts referenced above would be substantially equivalent to asubstantially rectangular hollow profile part due to the fact that sucha profile is a combination of two U-shaped parts, and that the strengthproperties would be determined by cross-sectioning the hollow profileinto a U-shaped part for testing purposes.

These and other modifications and variations of the present inventionmay be practiced by those of ordinary skill in the art, withoutdeparting from the spirit and scope of the present invention. Inaddition, it should be understood that aspects of the variousembodiments may be interchanged both in whole or in part. Furthermore,those of ordinary skill in the art will appreciate that the foregoingdescription is by way of example only, and is not intended to limit theinvention so further described in such appended claims.

1-31. (canceled)
 32. A method for forming a hollow profile that extendsin a longitudinal direction, the method comprising: impregnating aplurality of continuous fibers with a thermoplastic matrix within anextrusion device; consolidating the impregnated fibers to form a firstribbon in which the continuous fibers are oriented in the longitudinaldirection; pultruding the first ribbon and a plurality of long fibersthrough a die to form the hollow profile.
 33. The method of claim 32,wherein the continuous fibers, long fibers, or both, include glassfibers, carbon fibers, or a combination of glass and carbon fibers. 34.The method of claim 32, wherein the thermoplastic polymer matrixincludes a polyolefin, polyether ketone, polyetherimide, polyaryleneketone, liquid crystal polymer, polyarylene sulfide, fluoropolymer,polyacetal, polyurethane, polycarbonate, styrenic polymer, polyester,polyamide, or a combination thereof.
 35. The method of claim 32, whereinthe first ribbon has a void fraction of about 2% or less.
 36. The methodof claim 32, wherein a manifold assembly supplies the thermoplasticmatrix to the extrusion device, the manifold assembly comprisingbranched runners through which the thermoplastic matrix flows.
 37. Themethod of claim 32, wherein the profile exhibits a flexural modulus andmaximum flexural strength in the transverse direction, wherein the ratioof the flexural modulus to the maximum flexural strength is from about50 to about
 2200. 38. The method of claim 32, wherein the profileexhibits a flexural modulus of about 2 Gigapascals or more.
 39. Themethod of claim 32, wherein the profile exhibits a maximum flexuralstrength of about 12 Megapascals or more.
 40. The method of claim 32,wherein the long fibers are embedded within a second thermoplasticmatrix.
 41. The method of claim 40, wherein the second thermoplasticpolymer matrix includes a polyolefin, polyether ketone, polyetherimide,polyarylene ketone, liquid crystal polymer, polyarylene sulfide,fluoropolymer, polyacetal, polyurethane, polycarbonate, styrenicpolymer, polyester, polyamide, or a combination thereof.
 42. The methodof claim 32, wherein about 10% or more of the long fibers are orientedat an angle relative to the longitudinal direction.
 43. The method ofclaim 32, wherein the profile has a generally rectangular shape.
 44. Themethod of claim 32, wherein the long fibers are included within a firstlayer of the profile and the first ribbon is included within a secondlayer of the profile, the first layer being positioned adjacent to thesecond layer.
 45. The method of claim 44, wherein the first layer formsan inner layer of the hollow profile.
 46. The method of claim 45,wherein the second layer extends substantially around the periphery ofthe first layer.
 47. The method of claim 45, wherein the second layer islocated in one or more discrete regions adjacent to the first layer. 48.The method of claim 44, wherein the second layer forms an inner layer ofthe hollow profile.
 49. The method of claim 48, wherein the first layerextends substantially around the periphery of the second layer.
 50. Themethod of claim 48, wherein the first layer is located in one or morediscrete regions adjacent to the second layer.
 51. The method of claim32, wherein the cross-section shape of the profile is substantially thesame along the entire length of the profile.
 52. The method of claim 32,wherein the long fibers are included within the first ribbon.